Apparatus for grinding bifocal lenses.



B. MAYER: APPARATUS FOR GRINDING BIFOOAL LENSES.

, APPLICATION FILED Emma, 1936.

v91 4,59 1 Patented Mar. 9., 19%)2 5 wueuioz -Bl 3NJAMTIN MAYER, or BALTIMO E, MARYLAND.

'AJPARA'rUs Eon onmnmo nirocnn nnnsns.

Specification of Letters Patent.

Patented March 9 1909.

Application filed March 23, 1906. Serial No. 30Tt7d9.

Tool! whom itkmay ccaccrn:

' :Be ic'known that I, BENJAMIN MAYER, a

citizen of the United States, residing at Baltimore, in the State of Maryland, have mventedcertain new and useful Improvemeats in Ap ar'atus for Grinding Bifocal f ensesg of which the following is a specifica- 'Ti'lis invent-ion relates to improved appai-o rahus for grinding bifocal lenses.

The'-' ob 'ect of the invention is to provide improved means for retaining the lensholder from movement while the glass lens is belie" pressed upon the revolving grindmg dis The invent-ion is illustrated in the accom panyif ng drawing, in which,

'Figsrre 1 shows the apparatusin eleva tion', the emery an being insection. Fig,

26 fifisalplan View 0 the pin holder and grind ing disk Fig.- 3 isan end view of holdin Fig.4" shows the center pin in deta-i Fig; 5 i a view of the lens holder. Fig. 6

is a view/"of a solid or single-piece bifocal 2'5' lensasj-Inade by the improved, grinding apparatns, and shows the arched line which makes the" division between the two fields of the lens. The bifocal lens ground by'tlie apparatus herein shown, comprises a single piece of glass having two fiel'ds-a distance field, 0, and anear field, b, and the two fields separated by an arched division, a, which forms neither a crease nor a projecting ridge; ()p tical lenses of this style when worn scarcely show the arched division. This lens is de scribed in United States Letters Patent No.

798,435 granted to me August 29th, 1905.

The grinding disk, D, has on its upper 4c face two distinctgrinding surfaces, 9, and, h, which are closely adjoining, one being at the center and the other concentric or surrounding thefirst one.

The two grinding surfaces will always differ from each other, as for instance one maybe a. flat plane and the other convex or conca ve. A The smaller and. central grinding surface, 9, serves to grind the lower or near field of the lens, and the surrounding grind- ,50 in surface, h, grinds the u per or distance fie d of the lens. In the rawing for the mere purpose of illustration, the central grinding surface, g, is shown flatandthe same time concentric gi' indnig surface, h, is shown .by any well-known mechanism.

The lens hold'er comprises ablock, J, of suitable shape, which, in the present instance,

- has a side projecting portion with a hole, 70,-

through it. The holepfthe-block when the device is in operation is intended to be coincident with the axis or center of the grind-' ing disk, D, and the varying positions'wh-ich the hole may have in the block will govern the shape of the near or lower field, b, that will be produced onthe glass lens. The block must be of such size that when its hole,

; 7s, directly over the center of the disk, the

block pr perly overlap. onto both of the two grin-ding surfaces, g, Zn. It is to be understood that the glass lens. is to be se cured to the block, J,- in the. ordinary way, that is, by means-of cement In grinding, the lens which is cemented on the-lower side of the block, will have aportion in contact with the central grinding surface, g, and a dill'erentportion in contact with the other grinding surface, h, at the irheimprovar means devised to ret-ain the block or lens-holder, J, from vibratory or lateral movement while it is being-held by the hand and; also pressed upon'the revolving grinding disk, D, will now be described;

A; stifi-jbar, E, has one end firmly held in; a' box, m, which is secured by bolts to aring-shaped stand, N, which surrounds the run of the pan, 0. 'these grinding machines, surrounds the This pan, as-usual in grinding disk and collects the emery that would otherwise bescattered, The-bar, 'L,

fits snugly in the box, m, and is adjustable endwise therein, and set-screws, y), at one side of the box, and a set-screw, g, at an upper beveled corner of the box bear on the bar, L, and prevent it both from endwise movement and from vibration in the box which is important. The bar, L, extends over the grinding disk and at its free end holds a station ary stud or pin, Z, which points'downward and has position coincident with the-axis or center of the grinding disk. This stud or pin takes into the hole, k, of the lensblock and retains the latter from vibratory or lateral movement While the disk revolves, it being understood that the'operator will hold the lens-block, J with his hand and prevent it from revolving with the grinding disk, D. There is no revolnble movement of the pin, Z, but it has an up-and-down movement whereby to lift its end out of the hole, 70, or to enter its end intosaid hole.

Fig. 4 shows in detail'the construction of the pin and the'bolt whichcarries it. The pin, Z, projects down from a bolt, 1', which is vertically movable through the bar, L, a spiral spring, 5, is around that part of the bolt which projects below the bar and the action of the spring is to draw the bolt downward. The downward-pointing pin, Z, is fixed in the lower end of the bolt. From this description it will be. understood that the bolt, '1", may be raised against the clownpressure of the spring, 8, when it is desired to lift the pin, Z, out of the hole, is, in the lens block. As there is no revolution of the pin, Z, nor of the block, J, there will be no grinding or wear to result in either reducing the size of the pin or in. enlarging the size of the hole, it. Thus this construction obviates a serious defect existing in those grinding disks which have fixed at their center an upward-projecting pin to which the lensblock is loosely attached. In this last named. construction the disk and pin both revolve, and as the emery which is usually employed as an abrasive powder has free access to the parts where the pin turns in the hole of the lens-block, the said parts are rapidly cut by the emery and worn away so'th-at. after a' little wear accuracy of holding the lens-block eraser ing in combination a revoluble disk having two difierent grinding surfaces one, g, at the center and another, it, .surroundlng the said center; a r1g1dly-held bar extendlng over the said disk; a'pin held by said bar and pointing downward in a position co1n-.

cident with the axis of the said disk and with its lower end free, said pin capable of anup-and-down movement independent of the bar and without rotating, and a, lensholding block having at one side a hole w th which the said pin engages and said block voverlapping.the two grinding surfaces of the disk and requiring that the hand-of the operator must be applied directly to the" block to the lens.

A revoluble grinding disk for grinding bifocal lenses having. two distinct grinding surfacesone at the centerfor grinding the give the necessary down-pressure. on

near field and a difierent one concentric with the first-named for grinding the distance field; a lens-holder-which overlapsboth of said grinding surfaces; a box secured at an.

elevation above the, grinding disk; a bar extending over the grinding disk and held by said box and adjustable endwise therein; and a. vertical pin held rigidly by said bar and capable of' an up-and-down movement and its lower end engaging with said lensholder. I In testimony whereof I aflix my signature in presence of two witnesses.

' BENJAMEN MAYER. W'itnesses CHAS. B. Manx, Join \V. Hnwns. 

